In the prior art, functional and incircuit testing of complex printed circuit boards used in computer circuitry has been extremely costly and time-consuming. Functional testing of each board is accomplished by connecting the board under test to circuitry of a commercial main testing unit to place the printed circuit board (PCB) under power and then running the functional test or tests in accordance with a program or programs of the main or primary test unit. The incircuit or fault testing of the PCB is accomplished by means of a hand-held test probe brought into contact with a multitude of solder connections on the rear side of the PCB, one connection at a time, until the circuit integrity of the entire board is checked. This procedure is exceedingly slow and laborious, requiring up to twenty-four hours per board under test, in some cases. Consequently, the prior art PCB incircuit testing is very expensive. Furthermore, the commercial primary test unit costs as much as 1.5 million dollars, thus rendering the overall functional and incircuit testing of complex PCBs very costly. Some known commercial test facilities for complex PCBs require the use of as many as five of the primary test units for use with hand-operated test probes in carrying out the necessary functional and incircuit (fault) tests.
The objective of the present invention is to greatly simplify and reduce dramatically the cost of testing the complex PCBs, employed in computers and elsewhere. More particularly, the present invention seeks to provide an automated computer-controlled PCB test apparatus which is used in conjunction with the primary test unit in a much more expeditious and cost efficient manner in the performance of PCB functional and incircuit tests. As a result of the use of the test apparatus according to the invention, the number of primary test units required at certain test facilities can be reduced from five to two without any loss of production, in terms of numbers of PCBs being tested in a given period of time. This represents a savings of approximately 41/2 million dollars in capital equipment at a given test facility.
Furthermore, the PCB incircuit tests carried out by the apparatus in accordance with the present invention are not only faster but more thorough and more reliable compared to the prior art hand probe method. The test procedure carried out by the apparatus according to the invention can be widely varied under control of different computer programs employed with the primary test unit, thereby rendering the incircuit testing of complex PCBs highly versatile to meet the testing requirements of diverse types of boards.
In terms of the time required to complete the incircuit testing of some complex PCBs, this time can be reduced by means of the present invention by as much as fifteen hours in cases where twenty-four hours was previously required to hand probe the solder side of certain boards to test the integrity of the circuitry.